Presence information can be defined as the information pertaining to a person's availability to communicate at a given point in time. It may, for example, be used to evaluate a persons online status for instant messaging (IM) or other type of communication (e.g., online to receive email, do not disturb, offline).
A Presence Server can collect, store, and distribute status information about users (i.e., Presence Information). The information can originate from several different devices, for example from mobile phones, laptop computers, PDAs, desktop PCs, or even other application servers. The Presence Server can correlate this information to form a complete view of each user's presence information. It can then send the combined presence data to one or more “watchers” who have subscribed to the presence of a particular user. Thus, a Presence Server can act as an intelligent abstraction layer for communications related to presence performing functions such as:                1. managing connections from or sessions for authorized clients, servers, and other entities;        2. routing appropriately-addressed presence messages among such entities; and        3. receiving presence information from its clients and make this information available to entities (other clients) that subscribe to presence updates for a given set of clients.        
In modern business organizations it is not uncommon for groups of geographically dispersed individuals to participate in audio conferences, video conferences, data conferences (e.g., via NetMeeting or WebEx) or some combination thereof. Scheduling such conferences, e.g., coordinating contact times and equipment availability may at times be problematic. Furthermore, after a conference begins, current conference systems typically only notify the participants when a new “far end” joins or leaves the conference. No notification is given if another individual arrives at or departs from an already connected “far end.”
Therefore, what is needed is a system and method for adding presence information and extended presence information (defined below) to conferencing network devices, meeting locations and other multi-user devices to enhance user awareness of availability of shared resources. Furthermore, by extending presence information it may be possible to make users aware of capabilities of shared user devices and thus optimize meeting scheduling and use of corporate assets. Additionally, with extended presence information being shared amongst conferencing locations while conferencing is taking place, security may also be enhanced. This is because each location may be able to determine, in real-time or near real-time, exactly which individuals are present at each “far end” location even if these individuals arrive or leave during the conference.